When carrying out earthworks and especially excavation work, it is necessary to know where underground objects, such as supply lines laid underground, are buried, in order to prevent damage, for example to supply lines and/or to the earth-moving machines used. Often, these objects are incompletely or wrongly documented or not documented at all. Accordingly, the terrain to be worked must be investigated before the beginning of the earthworks with respect to underground objects. The investigation is effected in general on the basis of the detection of electromagnetic fields which can be coordinated with the objects, for example by means of commercially available hand-held locating devices.
However, such scanning of terrain is too time-consuming and expensive, in particular for the working of large areas. It is therefore usual to mount localization devices or locating devices, such as cable detectors, directly on the earth-moving machine—for example an excavator—and to detect the buried objects in the course of the ongoing earthworks. In order to be very certain to avoid encountering objects during excavation, locating devices by means of which the depth of the buried objects can also be determined are advantageously used. For this purpose, locating devices are known which have two antennae arranged a distance apart along a perpendicular to the object. The distance from the object to the locating device can be derived from the field conditions detected by means of the antennae and the known fixed spacing of the antennae. Advantageously, the object data are stored and recorded, with the result that terrain documentations, such as maps, can be prepared or supplemented.
Earth-moving machines, such as, for example, excavators, are sufficiently well known from the prior art. The invention relates to earth-moving machines having a working part—in particular an excavator arm—which has an earth-moving part, such as an excavator bucket. The earth-moving part is pivotably fastened, for example, to a lower boom component of the working part. In particular, the working part has two or three members as boom components, which can be moved by means of hydraulic adjustment mechanisms.
US 2006/0265914 A1 describes a system for monitoring a predetermined limit during earth-moving work which is carried out by an earth-moving machine. For this purpose, signal-transmitting devices which determine the limit or a limit range by their position are arranged in the terrain, in particular underground. By means of a receiver device, the signals emitted by the transmitting devices are received and are transmitted to an evaluation unit, the evaluation unit deriving a position of the signal-transmitting devices from the signals received and deriving information about the limit from said position. It is proposed to fasten the receiver device on the working machine itself or alternatively to position it in a mobile manner in a separate location from the working machine, for example on a further separate vehicle.
For use for locating, for example, an underground supply line generating a magnetic field, the system disclosed in US 2006/0265914 A1 is, however, unusable since, for detection of a supply line, requirements differing from a transmitter-receiver system are necessary.
U.S. Pat. No. 6,633,163 describes an earth-moving machine having two magnetic field detectors arranged at different heights on the machine. The comparison of the detector measurements provides information about the closeness of a field generator to the earth-moving machine. With the system described, the relative position of the field generator to the earth-moving machine is determined. The determination of the distance from the field generator to the earth-moving machine or the depth of the field generator is not mentioned in said US patent. Furthermore—owing to the arrangement of the detectors directly on the machine—the system is suitable only for earth-moving machines which pull a working part behind them.
U.S. Pat. No. 5,592,092 describes two sensors mounted a distance apart on the bucket of an excavator and intended for detecting magnetic fields of underground objects. From the known distance between the sensors, the difference between the detected field magnitudes and the bucket position, the distance from the bucket to the object is derived. Since the sensors are mounted on the excavator bucket, they are, depending on the bucket position, not perpendicularly above the object. The bucket position must therefore be taken into account when determining the distance. Moreover—owing to the fixing directly on the bucket—there is the danger that the sensors would be damaged during the excavation work.